1. Field of Invention
The present invention relates to a method of manufacturing a laminated coil device.
2. Description of Related Arts
A laminated coil power device can be one of laminated large-current ferrite chip beads, a laminated power inductor, and a laminated power transformer. Laminated coil devices are widely applied to the power cable of many kinds of portable products because it has the advantages of high reliability, may be mass produced, and is easily miniaturized and thinned.
Particularly, when the laminated coil power device uses ceramic materials, it is desirable to reach large impedance and inductance values while maintaining a small size and thinness of the end product, and in particular to have ultra-low DC resistance within the laminated coil power device so as to support a large current. Therefore, the laminated coil power device with a narrow and thick cross-section of the coil electrodes has been developed in order to reach the purposes mentioned above.
FIGS. 1 and 2 show the traditional laminated coil device comprising a ceramic insulating layer 202 with an electrode 201 directly printed thereon. In the traditional method, after the electrode paste is printed on the insulating layer 202, the electrode paste inevitably spreads out in a manner that makes it difficult to form a narrow and thick electrode. Because the area around the coils is minimal there is reduced impedance and inductance value of the end products. And as shown in FIG. 3, the traditional laminated coil device utilizes a multiple printing method to increase the thickness of the electrode 201, wherein when a plurality of thin sheets are stacked, the electrode printed on the surface of the insulating layer is raised. Thus the traditional laminated coil device may be characterized by a mismatch of the ceramic insulating layers 202 involving air spaces 203, which may short circuit the electrode, and result in lamination cracking, and delamination.
To solve the problems of the traditional laminated coil device, China Patent No. CN201138593Y discloses a product providing a plurality of coils connected in parallel, isolated with each other so as to reduce the resistance of the direct current of the ferrite chip beads. However, although the parallely-connected coils are able to reduce the impedance and inductance value of the product, the multiple parallely-connected coils exponentially increase the cost of the products, and have the limitation of a reduction of thickness.
Furthermore, Japanese Patent No. 11-97244 discloses a method of providing a plurality of coils connected in parallel and then integrated into a spiral-shaped coil so as to reduce the resistance of the direct current. Although this, on one hand, dramatically increases the length of the magnetic path and decreases the impedance and inductance value of the products, on the other hand, this method is high in cost, and has the limitation of thinning.